A software program for the head impulse testing device (HITD)

A comparison of functional vestibulo-ocular reflex and proprioception in athletes of combat sports and ball sports

Background

The contribution and role of sensory systems in providing postural control may vary depending on the condition or activity. Vestibulo-ocular reflex (VOR) and proprioception might be affected by the type of sport.

Objective

This study aimed to compare athletes engaged in combat sports and ball sports in terms of functional VOR and proprioception.

Design

This study is a cross-sectional, comperative research.

Method

Twenty-four athletes engaged in combat sports and 20 in ball sports were included in the study. Functional examination of VOR in athletes was performed with a novel Functional Head Impulse Test (fHIT). Proprioception analysis was evaluated using Laser Pointer Assisted Angle Reproduction Test (LPA-ART) in 90° shoulder flexion and abduction.

Results

fHIT lateral and posterior % Correct Answer (CA) values and anterior SCC 6000°/s² values of athletes engaged in ball sports were found to be statistically significantly higher than athletes in combat sports (p < 0.05). Except for anterior SCC 4000°/s² value, scores of the ball players in all accelerations and directions were higher than combat sports athletes, although it was not statistically significant. The 90° shoulder flexion and abduction angle deviation values obtained from the LI-ATT were statistically lower in those who played ball sports (p < 0.05).

Conclusions

Participation in sports branches played with the ball is expected to provide gains for athletes who want to reach high-level performance in proprioceptive and vestibular functioning and those with vestibular/proprioceptive pathology. Maintaining clear vision in dynamic sports branches can be improved by training VOR function.

The relationship between functional head impulse test and age in healthy individuals

BACKGROUND

fHIT is an easily applicable test battery that indirectly evaluates the vestibulo-ocular reflex (VOR) from a functional perspective.

AIMS/OBJECTIVES

The aim of this study was to Individuals determine the correlation between age and the percentage of correct answers (% CA) obtained in the functional head impulse test (fHIT) in healthy individuals.

MATERIAL AND METHODS

A total of 105 volunteers, 50 males and 55 females, between the ages of 18 and 70 years, participated in the study. A Beon Solution fHIT system (Zero Branco (TV), Italy) was used in the study.

RESULTS

In our study, a decrease in the mean % CA was observed in all semicircular canals (SCCs) with increasing age. Between age and mean % CA, a significant negative moderate (-0.311) correlation was observed in lateral SCCs, and a significant negative low (-0.257) correlation was observed in posterior SCCs (p <  0.05). In anterior SCCs, there was no statistically significant relationship between age and mean % CA (p >  0.05).

CONCLUSIONS

The present study performed in a healthy population will be helpful in terms of making comparisons in studies to be conducted in various vestibular diseases. It will also be a guide for identifying pathological consequences in vestibular diseases.

Vestibular Functioning in Children with Neurodevelopmental Disorders Using the Functional Head Impulse Test

Several studies in children with neurodevelopmental disorders (NDDs) including autism spectrum disorders (ASDs), reading impairment, or attention deficit/hyperactive disorder (ADHD) pointed toward a potential dysfunction of the vestibular system, specifically in its complex relationship with the cerebellum. The aim of the present study was to test the functional vestibulo-ocular reflex (VOR) responses in children with NDDs to measure functional performance of the vestibular system. The VOR is specifically involved in this stabilization of the image on the retina during rapid movements of the head. To perform this study, four groups of children with ASD, ADHD, reading impairment, and with neurotypical development (TD) were enrolled (n = 80). We performed the functional head impulse test (fHIT), which measured the percentage of correct responses by asking the child to identify an optotype briefly presented during passive head impulse in each direction of each semicircular canal plane. We observed significantly lower correct answers in children with NDDs compared with those with TD (p < 0.0001). Surprisingly, there was no significant difference between the three groups of children with NDDs. Our study fostered preliminary evidence suggesting altered efficiency of vestibular system in children with NDDs. VOR abnormalities estimated using the fHIT could be used as a proxy of NDD impairments in children, and represent a potential biomarker.

Functional Head Impulse Test in Professional Athletes: Sport-Specific Normative Values and Implication for Sport-Related Concussion

Dizziness, slow visual tracking, or blurred vision following active head (or body) movements are among the most common symptoms reported following sport-related concussion, often related to concurrent dysfunctions of the vestibular system. In some cases, symptoms persist even if bedside and auxiliary standard vestibular tests are unremarkable. New functional tests have been developed in recent years to objectify neurological alterations that are not captured by standard tests. The functional head impulse test (fHIT) requires the patient to recognize an optotype that is briefly flashed during head rotations with various angular accelerations (2,001–6,000 deg/s²) and assesses the proportion if correct answers (pca). 268 active professional athletes (23.70 ± 5.32y) from six different sports were tested using fHIT. Pca were analyzed both pooling head acceleration in the range of 2,001–6,000 deg/s² and computing a single pca value for each 1,000 deg/s² bin in the range 2,001–8,000 deg/s². No significant difference (p = 0.159) was found between responses to head impulses in the plane of horizontal (pca: 0.977) and vertical semicircular canals (pca: 0.97). The sport practiced had a major effect on the outcome of the fHIT. Handball players achieved a better performance (p < 0.001) than the whole athlete group, irrespective of the direction of head impulses. The pca achieved by athletes practicing snowboard, bob and skeleton were instead significantly below those of the whole athlete group (p < 0.001) but only when vertical head impulses were tested. Overall, pca declined with increasing head acceleration. The decline was particularly evident in the range not included in the standard fHIT exam, i.e., 6,001–8,000 deg/s² for horizontal and 5,001–8,000 deg/s² for vertical head impulses. When vertical head impulses were tested, athletes practicing snowboard, bob and skeleton (non-ball sports) showed, beside the lower overall pca, also a steeper decline as a function of vertical head acceleration. The findings suggest that: (1) functional VOR testing can help understanding sport-specific VOR requirements; (2) the fHIT is able to detect and objectify subtle, sport-specific changes of functional VOR performance; (3) if sport-specific normative values are used, the fHIT test procedure needs to be optimized, starting from the highest acceleration to minimize the number of head impulses.

The Functional Head Impulse Test to Assess Oscillopsia in Bilateral Vestibulopathy

Introduction: Bilateral vestibulopathy (BV) is a chronic condition in which vestibular function is severely impaired or absent on both ears. Oscillopsia is one of the main symptoms of BV. Oscillopsia can be quantified objectively by functional vestibular tests, and subjectively by questionnaires. Recently, a new technique for testing functionally effective gaze stabilization was developed: the functional Head Impulse Test (fHIT). This study compared the fHIT with the Dynamic Visual Acuity assessed on a treadmill (DVA_treadmill) and Oscillopsia Severity Questionnaire (OSQ) in the context of objectifying the experience of oscillopsia in patients with BV.

Methods: Inclusion criteria comprised: (1) summated slow phase velocity of nystagmus of <20°/s during bithermal caloric tests, (2) torsion swing tests gain of <30% and/or phase <168°, and (3) complaints of oscillopsia and/or imbalance. During the fHIT (Beon Solutions srl, Italy) patients were seated in front of a computer screen. During a passive horizontal head impulse a Landolt C optotype was shortly displayed. Patients reported the seen optotype by pressing the corresponding button on a keyboard. The percentage correct answers was registered for leftwards and rightwards head impulses separately. During DVA_treadmill patients were positioned on a treadmill in front of a computer screen that showed Sloan optotypes. Patients were tested in static condition and in dynamic conditions (while walking on the treadmill at 2, 4, and 6 km/h). The decline in LogMAR between static and dynamic conditions was registered for each speed. Every patient completed the Oscillopsia Severity Questionnaire (OSQ).

Results: In total 23 patients were included. This study showed a moderate correlation between OSQ outcomes and the fHIT [rightwards head rotations (r_s = −0.559; p = 0.006) leftwards head rotations (r_s = −0.396; p = 0.061)]. No correlation was found between OSQ outcomes and DVA_treadmill, or between DVA_treadmill and fHIT. All patients completed the fHIT, 52% of the patients completed the DVA_treadmill on all speeds.

Conclusion: The fHIT seems to be a feasible test to quantify oscillopsia in BV since, unlike DVA_treadmill, it correlates with the experienced oscillopsia measured by the OSQ, and more BV patients are able to complete the fHIT than DVA_treadmill.

Vestibulo-Ocular Responses and Dynamic Visual Acuity During Horizontal Rotation and Translation

Dynamic visual acuity (DVA) provides an overall functional measure of visual stabilization performance that depends on the vestibulo-ocular reflex (VOR), but also on other processes, including catch-up saccades and likely visual motion processing. Capturing the efficiency of gaze stabilization against head movement as a whole, it is potentially valuable in the clinical context where assessment of overall patient performance provides an important indication of factors impacting patient participation and quality of life. DVA during head rotation (rDVA) has been assessed previously, but to our knowledge, DVA during horizontal translation (tDVA) has not been measured. tDVA can provide a valuable measure of how otolith, rather than canal, function impacts visual acuity. In addition, comparison of DVA during rotation and translation can shed light on whether common factors are limiting DVA performance in both cases. We therefore measured and compared DVA during both passive head rotations (head impulse test) and translations in the same set of healthy subjects (n = 7). In addition to DVA, we computed average VOR gain and retinal slip within and across subjects. We observed that during translation, VOR gain was reduced (VOR during rotation, mean ± SD: position gain = 1.05 ± 0.04, velocity gain = 0.97 ± 0.07; VOR during translation, mean ± SD: position gain = 0.21 ± 0.08, velocity gain = 0.51 ± 0.16), retinal slip was increased, and tDVA was worse than during rotation (average rDVA = 0.32 ± 0.15 logMAR; average tDVA = 0.56 ± 0.09 logMAR, p = 0.02). This suggests that reduced VOR gain leads to worse tDVA, as expected. We conclude with speculation about non-oculomotor factors that could vary across individuals and affect performance similarly during both rotation and translation.

The functional head impulse test: preliminary data

The functional head impulse test is a new test of vestibular function based on the ability to recognize the orientation of a Landolt C optotype that briefly appears on a computer screen during passive head impulses imposed by the examiner over a range of head accelerations. Here, we compare its results with those of the video head impulse test on a population of vestibular neuritis patients recorded acutely and after 3 months from symptoms onset. The preliminary results presented here show that while both tests are able to identify the affected labyrinth and to show a recovery of vestibular functionality at 3 months, the two tests are not redundant, but complementary.

A New Tool for Investigating the Functional Testing of the VOR

Peripheral vestibular function may be tested quantitatively, by measuring the gain of the angular vestibulo-ocular reflex (aVOR), or functionally, by assessing how well the aVOR performs with respect to its goal of stabilizing gaze in space and thus allow to acquire visual information during the head movement. In recent years, several groups have developed clinical and quantitative approaches to functional testing of the vestibular system based on the ability to identify an optotype briefly displayed on screen during head rotations. Although the proposed techniques differ in terms of the parameters controlling the testing paradigm, no study has thus far dealt with understanding the role of such choices in determining the effectiveness and reliability of the testing approach. Moreover, recent work has shown that peripheral vestibular patients may produce corrective saccades during the head movement (covert saccades), yet the role of these eye movements toward reading ability during head rotations is not yet understood. Finally, no study has thus far dealt with measuring the true performance of their experimental setups, which is nonetheless likely to be crucial information for understanding the effectiveness of functional testing approaches. Thus we propose a new software and hardware research tool allowing the combined measurement of eye and head movements, together with the timing of the optotype on screen, during functional testing of the vestibulo-ocular reflex (VOR) based on the Head Impulse Test. The goal of such tool is therefore that of allowing functional testing of the VOR while collecting the experimental data necessary to understand, for instance, (a) the effectiveness of the covert saccades strategy toward image stabilization, (b) which experimental parameters are crucial for optimizing the diagnostic power of the functional testing approach, and (c) which conditions lead to a successful reading or an error trial.

A Device for the Functional Evaluation of the VOR in Clinical Settings

We developed the head impulse testing device (HITD) based on an inertial sensing system allowing to investigate the functional performance of the rotational vestibulo-ocular reflex (VOR) by testing its gaze stabilization ability, independently from the subject’s visual acuity, in response to head impulses at different head angular accelerations ranging from 2000 to 7000 deg/s². HITD was initially tested on 22 normal subjects, and a method to compare the results from a single subject (patient) with those from controls was set up. As a pilot study, we tested the HITD in 39 dizzy patients suffering, non-acutely, from different kinds of vestibular disorders. The results obtained with the HITD were comparable with those from the clinical head impulse test (HIT), but an higher number of abnormalities was detectable by HITD in the central vestibular disorders group. The HITD appears to be a promising tool for detecting abnormal VOR performance while providing information on the functional performance of the rotational VOR, and can provide a valuable assistance to the clinical evaluation of patients with vestibular disorders.